Weak battery condition signal from uninterruptible power supply

 

When the battery on the system falls below a specific level of charge, the uninterruptible power supply issues a weak battery condition signal.

The weak battery signal from the uninterruptible power supply will cause the system to perform a power loss controlled shutdown if the following conditions are true:

• You have chosen to use the four-wire communication between the System i™ product and an uninterruptible power supply.

• The utility fail signal is active.

The controlled shutdown occurs immediately. If the system is running on utility power and the uninterruptible power supply sends a weak battery signal, the system remains up and posts a CPIO964 message. However, the system initiates a shutdown mechanism immediately under this condition if utility power is lost.

A typical factory-preset time for an uninterruptible power supply to send a weak battery signal is with approximately two minutes of run time remaining. Some uninterruptible power supply models have an adjustable setting for this time. Ideally, you want to set it for the amount of time it takes for your system to perform a power-loss controlled shutdown. Do not assume that the factory-preset time on the uninterruptible power supply is sufficient for a normal shutdown of your system. Calculate the amount of time necessary to perform a power-loss controlled shutdown, use an appropriate value for QUPSDLYTIM, and adjust the time for weak battery signal on the uninterruptible power supply (if adjustable).

The figure shows the time progression of the QUPSDLYTIM function, from left to right.

Figure 1. Time line of QUPSDLYTIM function

The time line shows what happens from the time the power goes out to the time the system shuts down. The duration of the time is the same as the rated life of the battery. The time line starts at the point that utility power goes off. At the same time the uninterruptible power supply or battery power unit is active. At this time user program functions (if any) and the QUPSDLYTIM value time-out is in effect. When that time expires, main storage is saved, then shut down occurs. After that there should be some time left of battery life as a safety factor.

 

Parent topic:

Controlled shutdown concepts

Related concepts
Uninterruptible power supply delay time system value (QUPSDLYTIM) Uninterruptible power supply Planning for your physical environment

Related reference
Uninterruptible power supply messages